A pathologist enlisted by the FBI to reexamine the mysterious death of Chicago police Sgt. Donald Markham from a gunshot wound to the head states his case very clearly in a report released Thursday:

“His death should not be certified as a suicide,” as Chicago police detectives and the Cook County medical examiner determined soon after Markham’s body was discovered at his Far Northwest Side home on Sept. 2, 2015.

“The findings and observations at the scene of his death are inconsistent with a self-inflicted gunshot wound,” the FBI expert wrote. “The manner of death is best certified as a homicide, or death at the hands of another.”

The report, obtained by the Chicago Sun-Times through a public records request to Cook County government, was done by Dr. J. Scott Denton, a pathologist in downstate Bloomington who once served as Cook County’s interim medical examiner. His report was given to the FBI on Feb. 7, 2017, and subsequently to the medical examiner’s office in an effort to get that agency to reconsider its suicide ruling.

Among Denton’s findings:

• “The blood flow pattern” on Markham’s face “in the scene photos is inconsistent with the position of his head as shown.”

• “It is very concerning that the right hand and wrist are below and even partially under the left forearm that crosses over his chest . . . It is also very unreasonable to believe that Sgt. Markham was able to shoot himself in the right side of his head and then carry or transport the gun within his right hand to the left side of his body and cover it with his left arm . . . . Therefore the position of the gun in his right hand that is at the left side of his body . . . appears to have been manipulated after his death.”

• Markham’s fingers “showed no injuries or impression from the trigger guard.”

• With three of the Markhams’ five children at home, someone would have heard the gun fired: “It is difficult to understand how no one inside the house heard the gunshot wound unless an object muffled the sound of the gunshot.”

Dr. J. Scott Denton. | David Proeber / The Pantagraph

The FBI expert’s report takes aim at how the police and the medical examiner’s office reached the suicide conclusion: “It is also a matter of potential bias in the determination of manner of death that the scene investigation photographer’s placard and initial investigation reports all indicate that Sergeant Markham’s death was a suicide before a critical evaluation of the circumstances of his death was performed.

“In my experience, once a determination is established quickly at the scene,” Denton wrote, “it is difficult to change course and start an investigation over from the beginning without a preconceived and a continued confirmation bias, even after the autopsy and further investigation.”

He couldn’t be reached for comment Thursday.

The Chicago Police Department and the medical examiner’s office, headed by Dr. Ponni Arunkumar, have stood by their findings despite an extraordinary meeting last month at which the FBI urged it to reconsider.

In a nine-page response, dated Jan. 9, to the FBI expert’s findings, Arunkumar backed Dr. Stephen White’s original ruling that Markham shot himself in the head after an argument with his wife Dina Markham, who was also a Chicago cop.

Arunkumar — who once worked with Denton in the medical examiner’s office — took issue with his suggestion that the police influenced White to conclude that Donald Markham’s death was a suicide. She also questioned whether Denton was trying “to backfill a justification for a determination of homicide as a manner of death when the evidence is simply not there.”

And she disputed Denton’s assertions that Markham’s right hand under his left forearm indicated someone moved his body.

“Because body movement can occur after fatal gunshot wounds to the head . . . and are not evidence that the firearm was discharged by another person,” Arunkumar wrote. “It is not concerning that the right hand and wrist are below and even partially under the left forearm that crosses over his chest, as stated by the outside pathologist.”

Her office “re-reviewed” the case after meeting with the FBI, and the consensus of “more than 10 Cook County forensic pathologists . . . was that the body was not moved after the gunshot and that the clear preponderance of information and evidence supports the 2015 findings of the office, as well as the manner of death ruling of suicide.”

Markham, 51, who worked in the police narcotics division, was found dead in his bed in Old Norwood Park on the Far Northwest Side on Sept. 2, 2015, after arguing with his wife.

The police immediately treated his death as a suicide, removing the body and the bloody mattress on which it was found within three hours — even before the medical examiner’s office could examine the scene. Within weeks, authorities closed the case as a suicide.

Then, in December 2016, the FBI received a disc containing information on Markham’s death and a letter asking them to review the case, Denton says in his report.

The FBI enlisted Denton and an expert in bloodstain-pattern analysis to review the evidence.

That also prompted an investigation by the city of Chicago’s inspector general’s office into the police department’s actions that is ongoing.

Last May, Dina Markham told Sun-Times reporters she was unaware the FBI and inspector general were investigating. She drowned in her bathtub six days later, on May 28, after taking pills and drinking — a death the medical examiner ruled an accident.

The FBI won’t discuss the case.

Dina Markham was working in the police department’s Bureau of Internal Affairs at the time of her husband’s death. She was transferred 11 months later to the Area North detective division, then headed by Cmdr. Kevin Duffin, whose detectives had determined Donald Markham killed himself.

After the FBI began investigating and until the day she died, Dina Markham was exchanging text messages with Duffin, the Sun-Times has reported.

On the day she died, Duffin alerted the detectives investigating her death about the texts, which they had exchanged over six months.

Dina Markham and Donald Markham. | Facebook

Before Donald Markham died, the Markhams had been drinking at a bar, and they got into an argument, police reports say, when he wanted to go home because he had to work the next morning. They continued arguing at their home in the 5900 block of North Newark, the reports say.

According to those reports, Dina Markham told police she was locked out and had one of the couple’s five children let her in the house through a window. The reports say she was searching for her keys when she found her husband dead.

The Sun-Times previously has reported the case has been marked by a series of irregularities:

• Police didn’t test Dina Markham or anyone else who was at the Markhams’ home to determine whether they’d fired a weapon.

• Her husband’s body was driven to the county morgue by police officers, not by the private city contractor that normally transports bodies.

• The medical examiner’s office — which didn’t send anyone to the scene — has said the office wasn’t notified until Donald Markham’s body already was on the way to the morgue.

The Chicago Police Department’s Jefferson Park station. | Google

• About three hours after Dina Markham called 911, police lugged away the mattress, tossing it behind the Jefferson Park police station at 5151 N. Milwaukee. Someone called the Department of Streets and Sanitation ward superintendent, who sent out a crew for a special pickup. The mattress was in a garbage truck less than four hours after Markham’s wife’s call to 911.

• Duffin’s point person on Donald Markham’s case was Lt. Denis P. Walsh, under investigation at the time by the inspector general for irregularities in the case of David Koschman, the Mount Prospect man who died after being punched by Mayor Richard M. Daley’s nephew Richard “R.J.” Vanecko. Walsh resigned five months later to avoid being fired.